288 LETTER XXV. 



which inhabit water cxckisivcly, and appear at one 

 end of the scale of their developement in the form of 

 enormous Fuci, many fathoms in length, but at the 

 other as merely simple bladders sticking- together in 

 rows, are those to which I referred at the beginning 

 of this letter, as forming the link between the Animal 

 and Vegetable worlds. Like Lichens and Fungi, they 

 have reproductive organs of the most simple construc- 

 tion ; in those species which have the most complex 

 organization, the spores are stored up in peculiar re- 

 ceptacles, as in the larger and more perfect sea- weeds ; 

 but in others they are distributed vaguely through the 

 whole substance of the plant, and start into life when 

 liberated from their nests by the destruction of the in- 

 di\'idual that generated them. In the Lavers, whether 

 of fresh or salt water, they lie clustered in threes or 

 fours, in the substance of a green membrane ; in the 

 true Confervse they are nothing but granular matter, 

 locked up in little transparent tubes (Plate XXV. 2.). 

 It is of a vegetation of this latter kind that consist the 

 green slimy patches you see floating in water, or ad- 

 hering to stones and rocks from which water has re- 

 ceded. In Dr. Greville's Algae Britannicse, and in the 

 fifth volume of the English Flora, you will find a full 

 account of the genera and species of these singular 

 productions. 



What is most remarkable in them is their ap- 

 proach to the nature of animals, an approach which 

 is not only indicated by the apparently spontaneous 

 motions of the kinds called Oscillatoria, but in a much 

 more unequivocal manner by other kinds, if we can 



